Soft silicone hydrogel contact lenses are increasingly becoming popular because of their high oxygen permeability and comfort. But, a silicone hydrogel material typically has a surface, or at least some areas of its surface, which is hydrophobic (non-wettable) and susceptible to adsorbing lipids or proteins from the ocular environment and may adhere to the eye. Thus, a silicone hydrogel contact lens will generally require a surface modification.
A known approach for modifying the hydrophilicity of a relatively hydrophobic contact lens material is through the use of a plasma treatment, for example, commercial lenses such as Focus NIGHT & DAY™ and O2OPTIX™ (CIBA VISION), and PUREVISION™ (Bausch & Lomb) utilize this approach in their production processes. Advantages of a plasma coating, such as, e.g., those may be found with Focus NIGHT & DAY™, are its durability, relatively high hydrophilicity/wettability), and low susceptibility to lipid and protein deposition and adsorption. But, plasma treatment of silicone hydrogel contact lenses may not be cost effective, because the preformed contact lenses must typically be dried before plasma treatment and because of relative high capital investment associated with plasma treatment equipment.
Another approach for modifying the surface hydrophilicity of a silicone hydrogel contact lens is the incorporation of wetting agents (hydrophilic polymers) into a lens formulation for making the silicone hydrogel contact lens as proposed in U.S. Pat. Nos. 6,367,929, 6,822,016, 7,052,131, and 7,249,848. This method may not require additional posterior processes for modifying the surface hydrophilicity of the lens after cast-molding of silicone hydrogel contact lenses. However, wetting agents may not be compatible with the silicone components in the lens formulation and the incompatibility may impart haziness to the resultant lenses. Further, such surface treatment may be susceptible to lipid deposition and adsorption. In addition, such surface treatment may not provide a durable surface for extended wear purposes.
A further approach for modifying the hydrophilicity of a relatively hydrophobic contact lens material is a layer-by-layer (LbL) polyionic material deposition technique (see for example, U.S. Pat. Nos. 6,451,871, 6,717,929, 6,793,973, 6,884,457, 6,896,926, 6,926,965, 6,940,580, and 7,297,725, and U.S. Patent Application Publication Nos. US 2007/10229758A1, US 2008/0174035A1, and US 2008/0152800A1). Although the LbL deposition technique can provide a cost effective process for rendering a silicone hydrogel material wettable, LbL coatings may not be as durable as plasma coatings and may have relatively high densities of surface charges; which may interfere with contact lens cleaning and disinfecting solutions. To improve the durability, crosslinking of LbL coatings on contact lenses has been proposed in commonly-owned copending US patent application publication Nos. 2008/0226922 A1 and 2009/0186229 A1 (incorporated by reference in their entireties). However, crosslinked LbL coatings may have a hydrophilicity and/or wettability inferior than original LbL coatings (prior to crosslinking) and still have relative high densities of surface charges.
A still further approach for modifying the hydrophilicity of a relatively hydrophobic contact lens material is to attach hydrophilic polymers onto contact lenses according to various mechanisms (see for example, U.S. Pat. Nos. 6,099,122, 6,436,481, 6,440,571, 6,447,920, 6,465,056, 6,521,352, 6,586,038, 6,623,747, 6,730,366, 6,734,321, 6,835,410, 6,878,399, 6,923,978, 6,440,571, and 6,500,481, US Patent Application Publication Nos. 2009/0145086 A1, 2009/0145091A1, 2008/0142038A1, and 2007/0122540A1, all of which are herein incorporated by reference in their entireties). Although those techniques can be use in rendering a silicone hydrogel material wettable, they may not be cost-effective and/or time-efficient for implementation in a mass production environment, because they typically require relatively long time and/or involve laborious, multiple steps to obtain a hydrophilic coating.
Therefore, there is still a need for a method of producing silicone hydrogel contact lenses with wettable and durable coating (surface) in a cost-effective and time-efficient manner.